The invention relates to areal point-to-multipoint services in a mobile communication system and particularly to mapping of a logical name of a geographical destination area of a service to network element addresses in order to allow one and the same service request to be used for reaching service areas of even a plurality of service centres controlling point-to-multipoint services.
Mobile communication systems have been developed in an answer to a need to reach people when they are not at a fixed telephone terminal. With the increased use of various data transmission services in offices, different data services have been also introduced into mobile communication systems. Mobile communication networks, in turn, provide the user with an efficient access network to the actual data networks for mobile data transmission. For this purpose, various new forms of data services are being designed for existing and future mobile communication networks. Digital mobile communication systems, such as the pan-European mobile communication system GSM (Global System for Mobile Communication), support particularly well mobile data transmission.
The General Packet Radio Service GPRS is a new service in the GSM system and one of the objects of GSM Phase 2+ standardization at ETSI (European Telecommunication Standard Institute). The GPRS allows packet data transmission to be provided between mobile data terminals and external data networks, with the GSM network functioning as an access network. One of the requirements set to the GPRS is that it must interwork with different kinds of external data networks, such as the Internet or the X.25. In other words, the GPRS and the GSM network should be able to serve all users, irrespective of the data network the users wish to access through the GSM network. This means that the GSM network and the GPRS must support and process various kinds of network addressing and data packet formats. The processing of data packets also comprises their routing in the packet radio network. In addition, the users should be able to roam from the GPRS home network to another GPRS network, the operator backbone network of which may support a different protocol (CLNP, for example) than the home network (X.25, for example). The GPRS network architecture is illustrated in FIG. 1.
The GPRS service supports both point-to-point and point-to-multipoint transmissions. The function of a point-to-multipoint transmission is to allow a sender to transmit data to recipients in a destination area by using one and the same service request. The term ‘data’ in this application refers to any information relayed in a digital telecommunication system. The information may comprise digitized speech, inter-computer data traffic, telefax data, short program code segments, etc. The destination area is a geographical area determined by the sender either in the service request or when the initiation of a point-to-multipoint transmission is informed. The destination area can be determined either as a list of cells or a logical name. Since one logical name can be used to cover a large number of cells, most often the destination area is determined as a logical name. To control point-to-multipoint transmissions the GPRS network typically comprises a Point-To-Multipoint Service Centre PTM-SC, which is an essential element in the point-to-multipoint service. The centre receives service requests from a Service Requester and transmits the service to its service area. Actual point-to-multipoint services supported by the GPRS are Point-to-Multipoint Multicast PTM-M and Point-To-Multipoint Group Call PTM-G. A PTM multicast is broadcast in all the cells belonging to the destination area. A PTM group call is broadcast in the cells of the destination area in which at least one subscriber registered into the group is located.
A problem with the above described system is that it fails to determine how to map efficiently logical names in order to one or more network element addresses allowing the service to be transmitted to an entire geographical destination area that may cover a plurality of service areas of different packet radio networks or PTM service centres.